Hello and welcome to Healthcare Magic. Thanks for your query.
You partner may be having emotionally unstable or borderline personality traits which may be the reason for her mood instabilities, poor coping skills, low frustration tolerance and self-harming behaviour. I would advise you take her to a psychiatrist
for a detailed psychological assessment and further treatment. There are effective treatment options - in the form of medication or counselling
which can help can handle these emotional problems and depressive symptoms.
Wish you all the best.
- Dr. Jonas Sundarakumar